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extreme pressure sources

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: ALIHISGREAT » Mon Dec 10, 2007 4:47 pm

iknowmy3tables wrote:
ALIHISGREAT wrote:yeah i suppose, i presume you have the land for an air rifle so you can shoot them more frequently? (i'm jealous if you do :( )

hehe I'm probaly one of the luckiest ballistic enthusiast locally, for the most part It's dense suburbs around here but I live in a house with 1acre of land only one neighbor that can see my backyard, and the rest is state park forest, right in the middle of suburbia

back to subject anyone got some Ideas to expand on the pressure
i am now very jealous :(

and i don't quite understand the pressure washer idea could you please elaborate?
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Unread postAuthor: iknowmy3tables » Mon Dec 10, 2007 8:06 pm

its pretty simple, if you pump water into a chamber of air it will compress the air, why?: because the water in taking up the space in the tank pushing the air to the top,
why pressure washers? because they can produce really high water pressure (my dad's can reach 2800psi), so 2800psi of water pressure being pumped into a chamber can produce up to 2800psi of air pressure

why aren't high pressure air compressors as cheap as high pressure pressure washers?, because its not as easy to make a high pressure centrifugal pump (which is just a well machined blower, like in leaf blowers) for air, because air is too light for producing strong centripetal force, and is harder to seal and to be use as a coolant
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Unread postAuthor: MaxuS » Tue Dec 11, 2007 2:14 am

jackssmirkingrevenge wrote:
MaxuS wrote:I use one to pump up my PCP Air Rifle


Out of interest, what rifle is it, and legal limit or FAC?


Yeah, it is an Air Arms S410K, and the magazine is always a bit of a bugger, its smack on the legal limit at the moment. Although I am applying for an FAC, already have my Shotgun Certificate :D
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Unread postAuthor: ALIHISGREAT » Tue Dec 11, 2007 2:21 am

iknowmy3tables wrote:its pretty simple, if you pump water into a chamber of air it will compress the air, why?: because the water in taking up the space in the tank pushing the air to the top,
why pressure washers? because they can produce really high water pressure (my dad's can reach 2800psi), so 2800psi of water pressure being pumped into a chamber can produce up to 2800psi of air pressure

why aren't high pressure air compressors as cheap as high pressure pressure washers?, because its not as easy to make a high pressure centrifugal pump (which is just a well machined blower, like in leaf blowers) for air, because air is too light for producing strong centripetal force, and is harder to seal and to be use as a coolant


well it would work... probably the problams are in attaching the pressure washer to the air tank and the fact that your gun would be heavy after being partially filled with water and then surely you gun would shoot the water aswell and it would have masive recoil?

edit: i thought about this somemore and i think it would work better if you had the water pushing on a piston to compress the air so that there you be no water in the chamber. Then when fired the piston would go to the end of the chamber and you would need a bleeding system to get rid of the pressurized air behind the piston and something like a ball valve to empty the water through.
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Unread postAuthor: MaxuS » Tue Dec 11, 2007 2:46 am

I thought this had been brought up before, the liquid pilot volume. Getting it to seal well would be difficult under pressure though.
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Unread postAuthor: iknowmy3tables » Tue Dec 11, 2007 6:03 pm

MaxuS wrote:I thought this had been brought up before, the liquid pilot volume. Getting it to seal well would be difficult under pressure though.

I believe that was for pressurizing a hybrid (the generation x hybrid or something like that) but I don't think the usage of a pressure washer was involved with it, cause that can replace the whole combustion thing with such pressures

@ALIHISGREAT: I have been highly considering this Section 2.5

Analysis
Because a practical option for this setup might be a double acting hydraulic cylinder, (this might also help me reach more air pressure to get at least 3000psi of air from my 2800psi pressure washer if I used the side with cylinder’s rod since it has less area), however I still don’t think this is necessary since the whole pressure setup would probably be separate from my chamber to save money and avoid the huge change in volume, (unless I can possibly find a good high pressure air tank, since usually the ports on commercial air tanks are too small compared to they’re volume for an efficient spud gun)

The whole piston thing is still unnecessary because the water will separate itself from the air
edit: :shock: I forgot about the liquification of gasses at high pressures, shoot I'll have to research more, anyone know a the density of atmospheric gases in liquid form, for stuff like CO2 I can only find the gas and solid desity
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Unread postAuthor: ALIHISGREAT » Tue Dec 11, 2007 6:12 pm

yes but the water will be shot out of the launcher aswell or have i missed something?
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Unread postAuthor: DYI » Tue Dec 11, 2007 6:59 pm

Atmospheric air is composed of roughly 79% nitrogen, 20% oxygen, and 1% various other gases (mostly argon). Other than CO2, which makes up a very small fraction of atmospheric air, oxygen will be the first to liquify, at around 8kpsi, followed by nitrogen at 9 or 10 kpsi. You don't need to worry very much about liquification of the air.
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Unread postAuthor: Zen/// » Tue Dec 11, 2007 7:06 pm

its pretty simple, if you pump water into a chamber of air it will compress the air, why?: because the water in taking up the space in the tank pushing the air to the top,
why pressure washers? because they can produce really high water pressure (my dad's can reach 2800psi), so 2800psi of water pressure being pumped into a chamber can produce up to 2800psi of air pressure


He's talking about pumping water into a chamber squezzing the air in it.

why pressure washers? because they can produce really high water pressure (my dad's can reach 2800psi), so 2800psi of water pressure being pumped into a chamber can produce up to 2800psi of air pressure
NO, the pressure washer is capable of 2800psi of water pressure, just the size of the chamber will determine the air pressure, and the amount of water you pump in.

EDIT: if your wondering where i've been is that i've been playing warhawk on ps3
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Unread postAuthor: DYI » Tue Dec 11, 2007 7:09 pm

NO, the pressure washer is capable of 2800psi of water pressure, just the size of the chamber will determine the air pressure, and the amount of water you pump in.


Wrong. If the washer is capable of 2800 psi water pressure, it will be able to pump water into the chamber, compressing the air, until the air reaches 2800 psi, at which point the water won't be able to flow anymore.
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Unread postAuthor: Ragnarok » Tue Dec 11, 2007 7:15 pm

DYI wrote:Atmospheric air is composed of roughly 79% nitrogen, 20% oxygen, and 1% various other gases (mostly argon). Other than CO2, which makes up a very small fraction of atmospheric air, oxygen will be the first to liquify, at around 8kpsi, followed by nitrogen at 9 or 10 kpsi. You don't need to worry very much about liquification of the air.

Actually, that's not quite right.
Gasses will liquefy as a result of their own partial pressures, not the system pressure.

That means that in air, nitrogen will liquefy first, even before CO2, at about 12 kpsi, Oxygen will follow at 40 kpsi, and Argon and CO2 won't liquefy until you get into ridiculous pressures, because it's gas fraction is so low.

If this weren't the case, hybrids couldn't possibly exceed ~8x mixes.
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Unread postAuthor: DYI » Tue Dec 11, 2007 7:30 pm

Ah... I forgot about that somehow. It's been an ongoing argument for a while here, about propane liquifying at 8x+ mixes, so I didn't really know whether to believe the partial pressure thing or not.
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Unread postAuthor: iknowmy3tables » Wed Dec 12, 2007 3:45 pm

ALIHISGREAT wrote:yes but the water will be shot out of the launcher aswell or have i missed something?

my primary idea doesn't involve liquid water in the chamber,
but if i were: for the most part water does not compress into higher density, thus it will occupy the same area before during and after the the blast, the exception might be a higher water vapor concentration in the gas expelled which will increase recoil a little
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Unread postAuthor: ALIHISGREAT » Wed Dec 12, 2007 4:16 pm

iknowmy3tables wrote:
ALIHISGREAT wrote:yes but the water will be shot out of the launcher aswell or have i missed something?

my primary idea doesn't involve liquid water in the chamber,
but if i were: for the most part water does not compress into higher density, thus it will occupy the same area before during and after the the blast, the exception might be a higher water vapor concentration in the gas expelled which will increase recoil a little


surely the water will be 'sucked' out though?
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Unread postAuthor: iknowmy3tables » Wed Dec 12, 2007 11:01 pm

surely the water will be 'sucked' out though?

well what would replace the space if it did, when I suck water with a straw the water level goes down and into my mouth, but only because there is space for air to enter into the cup of water, so if I were to give you a drink pouch made from solid and completely sealed around the straw you couldn't drink from it unless you could get the pouch to crush

there is no input on the chamber to bring enough liquid or air to replace the water, the only case would be the possible change of pressure resulting in the water being "sucked into a lesser dense state to cover more area, which would be vapor and not the liquid I believe your talking about, so the canon would only expel humid air
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